High Even-Modulus Injection-Locked Frequency Dividers

This article designs and analyzes wide locking range (LR) high even-modulus LC-tank injection-locked frequency dividers (ILFDs) with current-reused topologies. The currentreused LC ILFD uses two stacked LC sub-ILFDs sharing the same dc current. The current-reused ILFD becomes a divide-by4 (÷4) ILFD, when both sub-ILFDs are used ÷2 ILFDs, and it is used as a divide-by-8 (÷8) ILFD when one sub-ILFD is used a +4 ILFD. Both sub-ILFDs use nMOSFETs as linear injection mixers for high conversion gain. For the ÷8 LC ILFD designed in the TSMC 0.18-μm CMOS process, the circuit uses one highfrequency ÷4 sub-ILFD and one low-frequency ÷2 sub-ILFD, at the supply of 1.6 V, and at the incident power of 0 dBm, the LR is 4 GHz (38.835%), from the incident frequency 8.3 to 12.3 GHz. The ÷8 ILFD core power consumption is 13.98 mW, and the die size is 1.2 × 1.2 mm
²
. Both the ÷8 LC ILFD and the ÷4 sub-ILFD have nonoverlapped and overlapped LRs, which are due to a dual-resonance resonator used in the varactor-free n-core sub-ILFD. The LC dual-resonance resonator is due to parasitic capacitors in active FETs and on-chip spiral inductors and inductive elements, and it is used to get wide overlapped LR. Two ÷4 LC ILFDs inherent in the designed circuit are also studied.